Electronic cigarette and method

ABSTRACT

An electronic smoking article includes a liquid supply including liquid material, a heater operable to heat the liquid material to a temperature sufficient to vaporize the liquid material and form an aerosol, a wick in communication with the liquid material and in communication with the heater such that the wick delivers the liquid material to the heater, and at least one air inlet operable to establish a predetermined resistance to draw under a prescribed test of said smoking article.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/593,004, filed on Jan. 31, 2012, the entire content of which is incorporated herein by reference thereto.

SUMMARY OF SELECTED FEATURES

An electronic cigarette or cigar (collectively “smoking article”) is provided which includes a heater element which vaporizes liquid material to produce an aerosol or “vapor”. The heater element preferably comprises a resistive heater coil, with a wick extending therethrough. The heater coil is constructed in a manner and formed from a material such that the production of hot spots and excessive temperatures are avoided during a puff.

The electronic article preferably includes a mouth end insert that includes at least two, diverging outlets to impart a fuller mouthfeel from the vapor output. Preferably, the aforementioned multi-ported mouth end insert cooperates with a gasket. Upon being drawn through the gasket, the vapor output enters a space just upstream of the mouthpiece which allows the air stream to expand and decelerate before entering the passages of the mouth piece insert so as to substantially avoid perceptions of “hot” at or about the lips of the “smoker”.

The electronic article preferably includes a metal case portion and a precision-formed primary, air inlet port at a location along the metal case portion, preferably along a metal side wall portion of the article. The air inlet port is precision-formed within close tolerances and the air inlet port is sized so as to be the predominating source of pressure drop along an air pathway of communication between the air inlet and the source of vapor (the heater). Such arrangement assures that RTD remains essentially the same from one puff to the next and from one article to the next. To further enhance consistent performance, RTD of an article is checked in the course of its manufacture, and corrective measure undertaken, if necessary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top planar view of an electronic cigarette according to a first embodiment;

FIG. 2 is a side cross-sectional view of the electronic cigarette shown in FIG. 1;

FIG. 3 a is an exploded, perspective view of elements comprising the cartridge section of the electronic cigarette shown in FIG. 1;

FIG. 3 b is a detailed view of an air inlet port of the cartridge section of the electronic cigarette shown in FIG. 1;

FIG. 4 is a perspective view of the mouth end insert of the electronic cigarette shown in FIG. 1;

FIG. 5 is a cross-sectional view along line A-A of the mouth end insert of FIG. 4;

FIG. 6 is a perspective view of an alternative embodiment of the mouth end insert of the electronic cigarette shown in FIG. 1;

FIG. 7 is a cross-sectional view along line B-B of the mouth end insert of FIG. 6;

FIG. 8 is an enlarged detail view of the heater assembly of the electronic cigarette shown in FIG. 1;

FIG. 9A is an enlarged view of the inner tube with a heater coil and wick assembly in position prior to positioning of a closure ring;

FIG. 9B is an enlarged view of the inner tube with a heater coil and wick assembly in position after positioning of a closure ring;

FIG. 10 is a cross-sectional view of a third embodiment of a mouth end insert for use with the electronic cigarette of FIG. 1;

FIG. 11 is an exploded view of the mouth end insert of FIG. 10;

FIG. 12 is a detailed view of an alternative connection arrangement assembly for use with the electronic cigarette of FIG. 1; and

FIG. 13 is a second embodiment of a connector cathode including a notch.

FIGS. 14A, 14B and 14C illustrate a third embodiment of a connector cathode including angled holes.

FIG. 15 is an illustration of a connector cathode and anode in which the anode is shortened to allow communication with air inlets.

FIG. 16 is a top view of an electronic cigarette including an aroma strip on an outer surface thereof.

FIG. 17 is a perspective view of a fourth embodiment of a mouth end insert for use with the electronic cigarette.

FIG. 18 is a cross-sectional view of an electronic cigarette according to the first embodiment and further including a sleeve assembly.

FIG. 19 is a side-view of an electronic cigarette according to another embodiment.

DETAILED DESCRIPTION Electronic Cigarette Layout

Referring to FIGS. 1 and 2, a novel electronic cigarette (article) 60 is provided and comprises a replaceable cartridge (or first section) 70 and a reusable fixture (or second section) 72, which in the preferred embodiment are coupled together at a threaded connection 205 or by other convenience such as a snug-fit, detent, clamp and/or clasp. Generally, the second section 72 includes a puff sensor 16 responsive to air drawn into the second section 72 via an air inlet port 45 adjacent the free end or tip of the cigarette 60, a battery 1 and control circuitry. The disposable first section 70 includes a liquid supply region of 22 of liquid and a heater 14 that aerosolizes liquid that is drawn from the liquid supply region 22 through a wick 28. Upon completing the threaded connection 205, the battery 1 is connectable with the electrical heater 14 of the first section 70 upon actuation of the puff sensor. Air is drawn primarily into the first section 70 through one or more air inlets 44.

In the preferred embodiment, once the liquid of the cartridge is spent, only the first section 70 is replaced. An alternate arrangement includes a layout where the entire article 60 is disposed once the liquid supply is depleted. In such case the battery type and other features might be engineered for simplicity and cost-effectiveness, but generally embodies the same concepts as in the preferred embodiment in which the second section is reused and/or recharged.

In a preferred embodiment, the electronic cigarette 60 is about the same size as a conventional cigarette. In some embodiments, the electronic cigarette 60 can be about 80 mm to about 110 mm long, preferably about 80 mm to about 100 mm long and about 7 mm to about 8 mm in diameter. For example, in a preferred embodiment, the electronic cigarette is about 84 mm long and has a diameter of about 7.8 mm.

Preferably, at least one adhesive-backed label is applied to the outer tube 6. The label completely circumscribes the electronic cigarette 60 and can be colored and/or textured to provide the look and/or feel of a traditional cigarette. The label can include holes therein which are sized and positioned so as to prevent blocking of the air inlets 44.

The outer tube 6 and/or the inner tube 62 may be formed of any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of those materials, or thermoplastics that are suitable for food or pharmaceutical applications, for example polypropylene, polyetheretherketone (PEEK), ceramic, and polyethylene. Preferably, the material is light and non-brittle.

Cartridge Structure

Referring now to FIGS. 1, 2 and 3 the first section 70 includes an outer tube (or casing) 6 extending in a longitudinal direction and an inner tube (or chimney) 62 coaxially positioned within the outer tube 6. Preferably, a nose portion 61 (see FIG. 3 a) of an upstream gasket (or seal) 15 is fitted into an upstream end portion 65 of the inner tube 62, while at the same time, an outer perimeter 67 of the gasket 15 provides a liquid-tight seal with an interior surface of the outer casing 6. The upstream gasket 15 also includes a central, longitudinal air passage 20, which opens into an interior of the inner tube 62 that defines a central channel 21. A transverse channel 33 at a backside potion of the gasket 15 intersects and communicates with the central channel 20 of the gasket 15. This channel 33 assures communication between the central channel 20 and a space 35 (see FIG. 2) defined between the gasket 15 and a cathode connector piece 37. In the preferred embodiment, the piece 37 includes a threaded section for effecting the threaded connection 205.

The cathode connector piece 37 includes opposing notches 38, 38′ about its perimeter 39, which, upon insertion of the cathode connector piece 37 into the casing 6, are aligned with the location of each of two RTD-controlling, air inlet ports 44 and 44′ in the outer casing 6. In an embodiment, such alignment may appear as shown in FIG. 3′(Detail). Such arrangement allows for placement of the ports 44, 44′ close to the threaded connection 205 without occlusion by the presence of the cathode connector piece 37. The arrangement also reinforces the area of ports 44, 44′ to facilitate precise drilling of the holes 44, 44′.

Air Inlets and Control of Resistance to Draw

In the preferred embodiment, at least one air inlet 44 is formed in the outer tube 6, preferably adjacent the threaded connection 205 to minimize the chance of a smoker' fingers occluding one of the ports and to control the resistance to draw (RTD) during smoking. Preferably, each of the RTD controlling, air inlets 44 and 44′ are machined into the casing 6 with precision tooling such that their diameters are closely controlled and replicated from one cigarette 60 to the next during their manufacture. Preferably, the air inlets 44 and 44′ are drilled with carbide drill bits or other high-precision tools and/or techniques. Also preferably, the outer tube 6 is formed of metal or metal alloys such that the size and shape of the air inlets 44, 44′ is not altered during manufacturing operations, packaging and smoking. Thus, the air inlets 44, 44′ provide consistent RTD. In the preferred embodiment, the air inlets 44, 44′ are sized and configured such that the electronic cigarette 60 has a RTD in the range of from about 60 mm H₂O to about 150 mm H₂O, more preferably about 90 mm H₂O to about 110 mm H₂O, most preferably about 100 mm H₂O to about 130 mm H₂O.

The RTD controlling, air inlets 44 and 44′ are the critical orifice (i.e. the smallest orifice along the pathway from the air inlets 44, 44′ and the inner passage 21 of the inner tube 62 (where the heater 14 aerosolizes liquid). Accordingly, the air inlets 44 and 44′ control the level of resistance to draw of the cigarette 60, which may be set at a level that contributes a drawing experience similar to that of drawing upon a conventional, lit-end cigarette.

Referring specifically to FIG. 1, another aspect of maintaining precise and reproducible resistance to draw is use of a metallic material in the casing 6 which is conducive to precision tooling and techniques. If another material is desired for the casing 6 (such as a plastic for presenting a softer feel), the air inlets 44, 44′ may be instead formed in a metallic plate fixture (or insert) 43 provided at the location of the air inlets 44, 44′ so as to maintain the precision of the air inlets 44, 44′.

It is envisioned that the metallic plate insert 43 may be included even in instances where the casing 6 is metallic, in that such arrangement allows the air inlets 44, 44′ to be produced and tested separately (off-line) on a collection of blank metallic plate inserts 43. Advantageously, should any finished metallic plate inserts 43 fail to meet standards or specifications for air inlet diameter (and RTD), the failed inserts may be disposed of instead of entire cartridge assemblies (first section) 70.

Referring back to FIG. 1, the metallic plate insert 43 may comprise a separate piece that becomes affixed to an outer surface of the casing 6 or wholly within the casing 6, in which case the outer casing 6 is preferably provided with an oversized hole, which can be superposed over the area of the air inlet 44. It is also envisioned that the insert might be shaped and fitted flush with the contour of the casing 6, using a snap fit and/or adhesive between the insert and the casing 6 or entirely within (internal of the outer casing 6). Preferably the shape and the location of the air inlet 44 of the insert 43 has a symmetry such that the air inlet 44 remains fully operative whether the insert 43 is positioned as shown in FIG. 1 or flipped 180 degrees. Moreover, the metallic plate insert 43 can be provided on an inside surface or on an outside surface of the outer casing 6. The metallic plate insert 43 can extend fully or partially about a circumference of the cigarette 60. When the metallic plate insert 43 extends partially about the circumference, multiple metallic plate inserts 43 can be used, each metallic plate insert 43 corresponding to a single air inlet 44, 44′.

In the preferred embodiment, the second section 72, includes an air inlet 45 at an upstream end 5 of the cigarette 60, which is sized just sufficient to assure proper operation of the puff sensor 16, located nearby. Drawing action upon the mouth end insert 8 is communicated to the air inlet port 45 through central channels provided in the anode post 47 c of the first section 70 and the anode connection post 47 b of the second section 72 and along space 13 between the battery 1 and the casing of the second section 72. These channels and the port 45 itself are sized such that the airflow rate there through are much smaller than through the air inlets 44, 44′, so that the impact on RTD is minimized and consistency in RTD is maintained. For example, each air inlet can be less than about 2.0 mm in width and less than about 1.5 mm in depth. For example, each air inlet can be about 0 7 mm to about 0.8 mm in width and about 0.7 mm to about 0.8 mm in depth. In a preferred embodiment, 95% of the air introduced in the cigarette 60 is through the air inlets 44, 44′, whereas only 5% of the total air flow enters through the inlet 45 at the upstream end 5 of the cigarette 60. Preferably, the ratio is determined by making a central channel 34 of the anode post 47 b of the second section 72 small enough to impart a pressure drop far greater than that of the air inlets 44, 44′. For example, the central channel 34 of the anode post 47 b may be sized to impart a pressure drop of approximately 2000 mm water (in contrast to a nominal pressure drop of 100 mm water from air inlets 44, 44′ combined).

Referring to FIG. 19, in order to maintain consistent RTD in the product, a removable protective covering 601 can be applied to the air inlets 44, 44′ to prevent degradation from dirt and dings during, manufacture, packaging shipping and handling at retail and beyond as shown in FIG. 19. To maintain consistent RTD until consumption, a circumferential wrapping or tape 601 may be wrapped about the outer casing 6 at the locations of the air inlets 44, 44′. In the alternative or in addition, the cigarette 60 may be accompanied with a reusable protective cover to provide the same or additional protections.

In addition, current manufacturing techniques for electronic cigarettes can be modified to include testing for consistent RTD. In other words, there is a need to couple an understanding of how to achieve consistent RTD in the product (as taught above) with an understanding of how to test for it in the course of manufacturing the product (as taught in the following). Achieving consistent RTD from one electronic cigarette to the next promotes consistent performance and delivery levels, and enhances smoking experiences by meeting smoker's expectations that a draw upon an electronic cigarette will be akin to drawing upon a lit end cigarette or cigar. The latter may include testing metallic plate inserts 43 prior to installation as previously described; or instead or in addition, testing completed first sections 70 by fastening a nominal, but inactivated second section 72 to a newly produced first section 70 to create a benign, inactive test configuration that accurately reproduces airflow event, but without risk of heater activation and applying a predetermined drawing action upon the configuration while measuring pressure drop. By way of non-limiting example, a fully assembled electronic cigarette may be drawn through the test configuration while pressure drop is measured using a PV 10 pressure drop instrument manufactured by Borgwaldt KC of Chesterfield, Va. A suitable pressure drop testing method for electronic cigarettes can be adopted from standard method ISO 6565:2011 entitled “Tobacco and tobacco products—Draw Resistance of Cigarettes and Pressure Drop of Filter Rods—Standard Conditions and Measurement”, and applied with instrumentation capable of measure pressure drop in a working range of 50 mmWG (mm water gauge) to 1900 mmWG and a diameter range of 5.0 mm to 9.0 mm. The test can be completed in a matter of seconds and the instrumentation can be calibrated to a range of 50 mmWG to 300 mmWG.

Instead of using an inactivated second section 72, it is envisioned that a releasable test body might be employed to serve the same purpose in a benign (inactive) test configuration. The test body would be configured to reproduce nominal impact of a real reusable second portion 72 upon RTD, but could be optimized for machine handing and high speed automated coupling to and removal from newly produced first sections 70 that are undergoing testing.

The inclusion of a threaded connection 205 does not facilitate automated, high speed machine handling and execution of the RTD tests. Referring now to FIG. 12, an alternative coupling 205′ may include connections comprising pins 501 and releasable detents 503 and/or electrical bearing surfaces 505 with releasable detents, rotational locking devices or the like. In the illustrated embodiment, the detent 503 cooperates with a raised annulus 509. In the alternative, one or more biased balls may be used in lieu of or in addition to the raised annulus 509. Such arrangements facilitate automated machine handling, provide a greater capacity for speedy yet accurate testing of RTD, and facilitate machine automated execution of RTD testing. It is envisioned that quality control during the drilling of orifices could include a feedback loop such that the RTD test results are monitored to detect trends away from specifications so that corrective measures may be undertaken, such as replacement of a worn drill bit.

Referring now to FIGS. 3 a and 3 b, preferably, the cathode connector piece 37 includes opposing notches 38, 38′ about its perimeter 39, which, upon insertion of the cathode connector piece 37 into the outer casing 6, are aligned with the location of each of two or more RTD-controlling, air inlets 44 and 44′ in the outer casing 6. In some embodiments, more than two air inlets 44, 44′ may be included (e.g., three, four, five, six, seven, eight, nine, ten or more). Alternatively, a single air inlet 44 can be included. In an embodiment, such alignment may appear as shown in FIG. 3 b. Such arrangement allows for placement of the air inlets 44, 44′ close to the threaded connection 205 without occlusion by the presence of the cathode connector piece 37. The arrangement also reinforces the area of air inlets 44, 44′, which can serve to facilitate precise drilling of the air inlets 44, 44′. Other arrangements can also be used as discussed below.

In another embodiment, as shown in FIG. 13, the cathode connector piece 37 can include one or more slits 300 formed in the perimeter 39 of the cathode connector piece 37. The outer casing 6 of the cartridge portion 70 is slid over the unthreaded end of the connector piece 37 until it reaches the stop (or edge) 307, leaving a predetermined portion of the slit 300 open to the exterior of the cartridge portion 70 for the admission of air. The admitted air can travel along the slit 300 and into the interior of the cartridge portion 70. The slit 300 may be used as the critical orifice and can be used in lieu of air inlets 44 and 44′. In another embodiment, the slit 300 may be used in addition to air inlets 44 and 44′.

In yet another embodiment, as shown in FIGS. 14A, 14B and 14C, the cathode connector piece 37 can include one or more angled holes 301 formed therein, which communicate with one or more slots 302 in a cathode connection fixture 49 b. Preferably, the cathode connection fixture 49 b can include an empty annular space 303 in an inner portion thereof which communicates with the one or more slots 302. Air is drawn in through slot 302 and travels into the annular space 303 and from there into the angled holes 307. Thus, there is no need to line up the slot 302 with the angled hole 301 because air will travel around the annular space 303 and into the angled holes 301 even if the holes 301 and slots 302 are not aligned. This arrangement provides advantages during manufacture since the angled holes 301 need not be aligned with the slots 302.

As shown in FIG. 15, in yet another embodiment, the anode post 47 c can be shortened as compared to the anode post 47 c of FIG. 2 so as to provide a larger air gap behind the cathode connector piece 37. Air enters via slot 302′ (not shown in FIG. 15 other than its relative position) and is drawn through an internal air inlet 44 via annular space 303 and then flows straight into the air gap, through the central channel 34 of the anode post 47 c and into the central channel 20 leading to the heater 14.

Liquid Supply Region, Heater and Wick

Preferably, a nose portion 93 of an downstream gasket 10 is fitted into a downstream end portion 81 of the inner tube 62. An outer perimeter 82 of the gasket 10 provides a substantially liquid—tight seal with an interior surface 97 of the outer casing 6. The downstream gasket 10 includes a central channel 84 disposed between the central passage 21 of the inner tube 62 and the interior of the mouth end insert 8 and which communicates aerosol from the central passage 21 to the mouth end insert 8.

The space defined between the gaskets 10 and 15 and the outer tube 6 and the inner tube 62 establish the confines of a liquid supply region 22. The liquid supply region 22 comprises a liquid material and optionally a liquid storage medium 210 operable to store the liquid material therein. The liquid storage medium 210 may comprise a winding of cotton gauze or other fibrous material about the inner tube 62.

In the preferred embodiment, the liquid supply region 22 is contained in an outer annulus 620 between inner tube 62 and outer tube 6 and between the gaskets 10 and 15. Thus, the liquid supply region 22 at least partially surrounds the central air passage 21. The heater 14 extends transversely across the central channel 21 between opposing portions of the liquid supply region 22.

Preferably, the liquid storage medium 210 is a fibrous material comprising cotton, polyethylene, polyester, rayon and combinations thereof. Preferably, the fibers have a diameter ranging in size from about 6 microns to about 15 microns (e.g., about 8 microns to about 12 microns or about 9 microns to about 11 microns). The liquid storage medium 210 can be a sintered, porous or foamed material. Also preferably, the fibers are sized to be irrespirable and can have a cross-section which has a y shape, cross shape, clover shape or any other suitable shape. In the alternative, the liquid supply region 22 may comprise a filled tank lacking a fibrous storage medium 21 and containing only liquid material.

Also preferably, the liquid material has a boiling point suitable for use in the electronic cigarette 60. If the boiling point is too high, the heater 14 will not be able to vaporize liquid in the wick 28. However, if the boiling point is too low, the liquid may vaporize even when the heater 14 is not being activated.

Preferably, the liquid material includes a tobacco-containing material including volatile tobacco flavor compounds which are released from the liquid upon heating. The liquid may also be a tobacco flavor containing material or a nicotine-containing material. Alternatively, or in addition, the liquid may include a non-tobacco material. For example, the liquid may include water, solvents, ethanol, plant extracts and natural or artificial flavors. Preferably, the liquid further includes an aerosol former. Examples of suitable aerosol formers are glycerine and propylene glycol.

Referring now also to FIG. 8, in use, liquid material is transferred from the liquid supply region 22 and/or liquid storage medium 210 in proximity of the 14 heater by capillary action of the wick 28. In one embodiment, the wick 28 has a first end portion 29 and a second end portion 31 as shown in FIG. 8. The first end 29 and the second end 31 extend into opposite sides of the liquid storage medium 21 for contact with liquid material contained therein. Also preferably, the heater 14 at least partially surrounds a central portion 113 of the wick 28 such that when the heater 14 is activated, the liquid in the central portion 113 of the wick 28 is vaporized by the heater 14 to form an aerosol. The wick 28 preferably comprises filaments having a capacity to draw a liquid, more preferably a bundle of glass (or ceramic) filaments and most preferably a bundle comprising a group of windings of glass filaments, preferably three of such windings, all which arrangements are capable of drawing liquid via capillary action via interstitial spacings between the filaments. Preferably, the wick 28 is flexible and includes three strands, each strand including a plurality of filaments. Moreover, it is noted that the end portions of the 29 and 31 of the wick 28 are flexible and foldable into the confines of the liquid supply region 22.

Advantageously, the liquid material in the liquid supply region 22 is protected from oxygen (because oxygen cannot generally enter the liquid supply region 22 via the wick 28). In some embodiments, the liquid material is also protected from light so that the risk of degradation of the liquid material is significantly reduced. Thus, a high level of shelf-life and cleanliness can be maintained.

In the preferred embodiment, the liquid supply region 22 is sized and configured to hold enough liquid material such that the electronic cigarette 60 is operable for smoking for at least about 200 seconds, preferably at least about 250 seconds, more preferably at least 300 seconds and most preferably at least about 350 seconds. Thus, liquid supply region 22 is equivalent to about one pack of traditional cigarettes. Moreover, the electronic cigarette 60 can be configured to allow each puff to last a maximum of about 5 seconds.

Mouth End Insert

Referring to FIGS. 2, 3 a, 4, 5, 6, 7 and 17, the first section 70 includes a mouth end insert 8 having at least two diverging outlet passages 24 (e.g., preferably 2 to 6 outlet passages 24, more preferably 4 outlet passages 24). Preferably, the outlet passages 24 are located off-axis and are angled outwardly in relation to the central channel 21 of the inner tube 62 (i.e., divergently). Also preferably, the mouth end insert (or flow guide) 8 includes outlets 24 uniformly distributed about the perimeter of mouth end insert 8 so as to substantially uniformly distribute aerosol in a smoker's mouth during use and create a greater perception of fullness in the mouth. Thus, as the aerosol passes into a smoker's mouth, the aerosol enters the mouth and moves in different directions so as to provide a full mouth feel. In contrast, electronic cigarettes having a single, on-axis orifice tend to direct its aerosol as single jet of greater velocity toward a more limited location within a smoker's mouth.

In addition, the diverging outlet passages 24 are arranged and include interior surfaces 83 such that droplets of unaerosolized liquid material, if any, that may be entrained in the aerosol impact the interior surfaces 83 of the mouth end insert 8 and/or impact portions of walls 305 which define the diverging outlet passages 24. As a result such droplets are substantially removed or broken apart, to the enhancement of the aerosol.

In the preferred embodiment, the diverging outlet passages 24 are angled at about 5° to about 60° with respect to the longitudinal axis of the outer tube 6 so as to more completely distribute aerosol throughout a mouth of a smoker during use and to remove droplets. In a preferred embodiment, there are four diverging outlet passages 24 each at an angle of about 40° to about 50° with respect to the longitudinal axis of the outer tube 6, more preferably about 40° to about 45° and most preferably about 42°.

Preferably, each of the diverging outlet passages 24 has a diameter ranging from about 0.015 inch to about 0.090 inch (e.g., about 0.020 inch to about 0.040 inch or about 0.028 inch to about 0.038 inch). The size of the diverging outlet passages 24 and the number of diverging outlet passages 24 can be selected to adjust the resistance to draw (RTD) of the electronic cigarette 60, if desired.

In one embodiment shown in FIG. 17, the mouth end insert 8 can include diverging outlet passages 24 and an on-axis outlet passage 26.

As shown in FIG. 2, an interior surface 83 of the mouth end insert 8 can comprise a generally domed surface 83. Alternatively, as shown in FIG. 7, the annular interior surface 83′ of the mouth end insert 8 can be generally cylindrical or frustoconical, with a planar end surface. Preferably, the interior surface 83 is substantially uniform over the surface thereof. Moreover, the interior surface 83 can be symmetrical about the longitudinal axis of the mouth end insert 8. However, in other embodiments, the interior surface 83 can be irregular and/or have other shapes.

In a preferred embodiment, a hollow 911 is disposed at the convergence of the diverging outlet passages 24 within the mouth end insert 8

The mouth end insert 8 may be integrally affixed within the tube 6 of the cartridge 70.

As mentioned previously, the multi-port mouth end insert 8 disperses and changes the direction of the aerosol as it is drawn from the electronic cigarette 60 so as to provide a fuller mouth feel. As aerosol is formed, it passes through the central channel 21 in the inner tube 62 and through the central channel 84 in the downstream gasket 10. In panel testing of early prototypes, some panelists reported a “hot” sensation on the lips from smoking an electronic cigarette constructed to include a mouth end insert including a plurality of diverging outlet passages 24 and a central channel 84 having a diameter of about 1.3 mm. However, in electronic cigarettes in which the inside diameter of the central channel 84 was increased to about 2.6 mm, reports of “hot” sensations essentially ceased.

Dynamic modeling of the area at and about the downstream gasket 10 and the mouth end insert 8 has indicated that a small 1 mm wide central channel 84 at the gasket 10 tends to create peak velocities of approximately 12 meters per second (m/sec) in aerosol exiting the mouth end insert. In contrast, modeling of a system including a 5 mm wide central channel 84 indicates peak velocities of only 2.5 m/s is achieved at the exits of the diverging outlet passages 24 of the mouth end insert 8, which is approximately a five-fold decrease in air velocity. From the aforementioned testing and modeling it is believed a further improvement in the organoleptic experience with an electronic cigarette is achieved by preventing acceleration of the aerosol flow stream by increasing the diameter of the central channel 84 before it is drawn through the exits of the diverging outlet passages 24 of the multi-port mouth end insert 8.

Accordingly, it is advantageous to provide an electronic cigarette having a downstream gasket 10 having a central channel 84, which has a diameter sufficient to prevent acceleration of the aerosol flow stream before reaching the mouth end insert 8. Preferably, the diameter of the central channel 84 is about 2.0 mm to about 3.0 mm, more preferably about 2.4 mm to about 2.8 mm. The mouth end insert 8 then divides output from the central channel 84 into multiple divergent streams of reduced speed so as to provide a full mouth feel and to avoid sensations of “hot”.

In that an appropriately sized central channel 84 of the gasket 10 serves to substantially prevent acceleration of the aerosol, such functionality can be further enhanced by providing the exit orifice with a beveled rim (not shown) at its exit plane to further reduce speed of the aerosol before it reaches the mouth end insert 8.

In an alternative embodiment, the mouth end insert 8 and the downstream gasket 10 can be integrally formed as a single piece so as to enhance consistent performance and to facilitate manufacture.

As shown in FIGS. 10 and 11, in an alternative embodiment, the electronic cigarette 60 of FIG. 1 can include a mouth end insert 8 having a stationary piece 27 and a rotatable piece 25. Outlets 24, 24′ are located in each of the stationary piece 27 and the rotatable piece 25. The outlets 24, 24′ match up as shown to allow aerosol to enter a smoker's mouth. However, the rotatable piece 25 can be rotated within the mouth end insert 8 so as to at least partially block one or more of the outlets 24 in the stationary mouth end insert 28. Thus, the consumer can adjust the amount of aerosol drawn with each puff. The outlets 24, 24′ can be formed in the mouth end insert mouth end insert 8 such that the outlets 24, 24′ diverge to provide a fuller mouth feel during inhalation of the aerosol.

Circuitry, Alloys Improving Consistent Heater Performance, Hot Spots and Carbonyl Abatement

In the preferred embodiment, the power supply 1 includes a battery arranged in the electronic cigarette 60 such that the anode 47 a is downstream of the cathode 49 a. A battery anode post 47 b of the second section 72 preferably contacts the battery anode 47 a.

More specifically, electrical connection between the anode 47 a of the battery 1 and the heater coil 14 in the first section 70 is established through a battery anode connection post 47 b in the second section 72 of the electronic cigarette 60, an anode post 47 c of the cartridge 70 and an electrical lead 47 d connecting a rim portion of the anode post 47 c with an electrical lead 109 of the heater element 14 (see FIG. 8). Likewise, electrical connection between the cathode 49 a of the battery 1 and the other lead 109′ of the heater coil 14 is established through the threaded connection 205 between a cathode connection fixture 49 b of the second portion 72 and the cathode connector piece 37 of the first section 70 and from there through an electrical lead 49 c which electrically connects the fixture 37 to the opposite lead 109′ of the heater coil 14.

Preferably, the electrical leads 47 d, 49 c and the heater leads 109, 109′ are highly conductive and temperature resistant while the coiled section 110 of the heater 14 is highly resistive so that heat generation occurs primarily along the coils 110 of the heater 14. Also preferably, the electrical lead 47 d is connected to the heater lead 109 by crimping. Likewise, the electrical lead 49 c is connected to the heater lead 109′ by crimping. In an alternative embodiment, the electrical leads 47 d, 49 c can be attached to the heater leads 109, 109′ via soldering. Crimping is preferred as it speeds manufacture.

The battery can be a Lithium-ion battery or one of its variants, for example a Lithium-ion polymer battery. Alternatively, the battery may be a Nickel-metal hydride battery, a Nickel cadmium battery, a Lithium-manganese battery, a Lithium-cobalt battery or a fuel cell. In that case, preferably, the electronic cigarette 60 is usable by a smoker until the energy in the power supply is depleted or in the case of lithium polymer battery, a minimum voltage cut-off level is achieved.

Alternatively, the power supply 1 may be rechargeable and include circuitry allowing the battery to be chargeable by an external charging device. In that case, preferably the circuitry, when charged, provides power for a pre-determined number of puffs, after which the circuitry must be re-connected to an external charging device. To recharge the electronic cigarette 60, an USB charger or other suitable charger assembly can be used.

Preferably, the electronic cigarette 60 also includes control circuitry including a puff sensor 16. The puff sensor 16 is operable to sense an air pressure drop and initiate application of voltage from the power supply 1 to the heater 14. As shown in FIG. 2, the control circuitry can also include a heater activation light 48 operable to glow when the heater 14 is activated. Preferably, the heater activation light 48 comprises an LED and is at an upstream end of the electronic cigarette 60 so that the heater activation light 48 takes on the appearance of a burning coal during a puff. Moreover, the heater activation light 48 can be arranged to be visible to the smoker. In addition, the heater activation light 48 can be utilized for cigarette system diagnostics or to indicate that recharging is in progress. The light 48 can also be configured such that the smoker can activate and/or deactivate the light 48 for privacy, such that the light 48 would not activate during smoking if desired.

Preferably, the at least one air inlet 45 (FIG. 1) is located adjacent the puff sensor 16, such that the puff sensor 16 senses air flow indicative of a smoker taking a puff and activates the power supply 1 and the heater activation light 48 to indicate that the heater 14 is working.

A control circuit is preferably integrated with the puff sensor 16 and supplies power to the heater 14 responsive to the puff sensor 16, preferably with a maximum, time-period limiter.

Alternatively, the control circuitry may include a manually operable switch for a smoker to initiate a puff. The time-period of the electric current supply to the heater may be pre-set depending on the amount of liquid desired to be vaporized. Alternatively, the circuitry may supply power to the heater 14 as long as the puff sensor 16 detects a pressure drop.

Preferably, when activated, the heater 14 heats a portion of the wick 28 surrounded by the heater for less than about 10 seconds, more preferably less than about 7 seconds. Thus, the power cycle (or maximum puff length) can range in period from about 2 seconds to about 10 seconds (e.g., about 3 seconds to about 9 seconds, about 4 seconds to about 8 seconds or about 5 seconds to about 7 seconds).

Preferably, the heater 14 is a wire coil that surrounds the wick 28. Examples of suitable electrically resistive materials include titanium, zirconium, tantalum and metals from the platinum group. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel. For example, the heater can be formed of nickel aluminide, a material with a layer of alumina on the surface, iron aluminide and other composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required. Preferably, the heater 14 comprises at least one material selected from the group consisting of stainless steel, copper, copper alloys, nickel-chromium alloys, super alloys and combinations thereof. In a preferred embodiment, the heater 14 is formed of nickel-chromium alloys or iron-chromium alloys, although the latter is not preferred for reasons which follow. In another embodiment, the heater 14 can be a ceramic heater having an electrically resistive layer on an outside surface thereof.

In another embodiment, the heater 14 may be constructed of an iron-aluminide (e.g., FeAl or Fe₃Al), such as those described in commonly owned U.S. Pat. No. 5,595,706 to Sikka et al. filed Dec. 29, 1994, or nickel aluminide (e.g., Ni₃Al). Use of iron-aluminide is advantageous in that iron-aluminide exhibits high resistivity. FeAl exhibits a resistivity of approximately 180 micro-ohms, whereas stainless steel exhibits approximately 50 to 91 micro-ohms. The higher resistivity lowers current draw or load on the power source (battery) 1.

In the preferred embodiment, the heater coil 14 is formed from a nickel—chromium alloy that is essentially free of iron content. Experience has indicated that heater coils constructed from an iron chromium alloy suffered oxidation of their iron content if the alloys were contacted with water during manufacturing operations, during shelf-life and/or operation of the device.

It is known that heating glycerin and/or propylene glycol beyond certain temperatures produces carbonyls (which include formaldehydes). Iron oxide tends to catalyze these reactions such that carbonyls are produced at lower temperatures. By using alloys essentially free of iron content, such catalyzation is avoided and the possibility of producing carbonyls and other constituents is minimized.

Moreover, in the manufacture and design of the preferred embodiment, certain aspects and measures are employed to avoid occurrence of unintended “hot spots” in the heater coil 14 during its heating cycle. Hot spots may contribute excessive peak temperatures that may produce undesired constituents that would otherwise be avoided in the absence of a hot spot.

While not wishing to be bound by theory, it is believed that if a winding of a coil heater 14 is altered such that spacing between loops of the coil 14 is locally reduced, the reduced spacing will create hotspots that are believed to drive peak temperatures beyond desirable levels. It is also believed that establishing uniform spacing along the coils of the heater 14 and taking steps to preserve the original, uniform spacing in the winding of the coil heater 14 will avoid the consequences of “hot spots”.

In particular and referring to FIG. 8, it is envisioned that production of consistent coil spacing 111 throughout the coiled section 110 of a given heater coil 14 may be achieved in ways including using automated winders to wind the coil about the wick 28 and using the wick 28 as an arbor for the winding step. In the preferred embodiment 3 to 8 windings are preferred, more preferably, 3 to 5 windings.

Once established, the uniformity of the coil spacing 111 is preserved in the course of manufacture and in the design of the preferred embodiment.

Referring also to FIG. 9A, in particular, the provision of opposing slots 63 in the inner tube 62 facilitates placement of the heater 14 and wick 28 into position within the inner tube 62 without impaction between edges of the slots 63 and the coiled section 110 (shown in FIG. 8) of the heater 14. Accordingly, edges of the slots 63 are not allowed to impact and alter the coil spacing 111 of the heater 14, which would otherwise create potential sources of hotspots.

Referring now to FIG. 9B, care is taken to position a closure ring 69 such that it is proximate to or touches but does not urge against the wick 28. Such positioning avoids imposing bending moments upon the heater coil 14 and avoids bowing of the coil 14 which might otherwise produce hotspots along one side of the coil 14 where the coil spacing 111 would become compressed and reduced. Thus, the upstream edge 114 of the closure ring 69 is brought into proximity of the wick 28, but is not positioned over the wick 28 so as to avoid the possibility of the aforementioned bowing effect. The closure ring 69, when placed as shown in FIG. 9B, closes off a remainder of open space provided between the heater coil assembly and the slot 63.

In the preferred embodiment, the inner tube 62 and the closure ring 69 are constructed from woven fiberglass.

In the preferred embodiment, the inner tube 62 has a diameter of about 4 mm and each of the opposing slots 63 has major and minor dimensions of about 2 mm by about 4 mm.

In one embodiment, the heater 14 comprises a wire coil which at least partially surrounds the wick 28. In that embodiment, preferably the wire is a metal wire and/or the heater coil may extend fully or partially along the length of the wick 28. The heater coil 14 may extend fully or partially around the circumference of the wick 28. In another embodiment, the heater coil is not in contact with the wick 28.

Preferably, the heater 14 heats liquid in the wick 28 by thermal conduction. Alternatively, heat from the heater 14 may be conducted to the liquid by means of a heat conductive element or the heater 14 may transfer heat to the incoming ambient air that is drawn through the electronic cigarette 60 during use, which in turn heats the liquid by convection.

In one embodiment, the wick 28 comprises a ceramic wick of ceramic filaments having a capacity to draw a liquid. As noted above, the wick 28 is at least partially surrounded by the heater 14. Moreover, in the preferred embodiment, the wick 28 extends through opposed slots 63 in the inner tube 62 such that each end of the wick 28 is in contact with the liquid supply region 22 (shown in FIG. 2).

In the preferred embodiment, the wick 28 comprises filaments and comprises a bundle of glass filaments. For example, the wick 28 may include a plurality of filaments. The filaments or threads may be generally aligned in a direction perpendicular (transverse) to the longitudinal direction of the electronic cigarette. Preferably, the wick 28 includes 1 to 8 filaments, more preferably 2 to 6 filaments. In the preferred embodiment, the wick 28 includes 3 stands, each strand comprising a plurality of glass filaments twisted together.

In the preferred embodiment, the structure of the wick 28 is formed of filaments through which the liquid can be transported to the heater 14 by capillary action. The wick 28 can include filaments having a cross-section which is generally cross-shaped, clover-shaped, Y-shaped or in any other suitable shape.

Preferably, the wick 28 includes any suitable material or combination of materials. Examples of suitable materials are glass, ceramic- or graphite-based materials. Moreover, the wick 28 may have any suitable capillarity drawing action to accommodate aerosol generating liquids having different liquid physical properties such as density, viscosity, surface tension and vapor pressure. The capillary properties of the wick 28, combined with the properties of the liquid, ensure that the wick 28 is always wet in the area of the heater 14 to avoid overheating of the heater 14.

Instead of using a wick 28, the heater 14 can be a porous material which incorporates a resistance heater formed of a material having a high electrical resistance capable of generating heat quickly.

Preferably, the wick 28 and the fibrous medium of the liquid supply region 22 are constructed from glass fiber.

Sleeve Assembly

As shown in FIG. 18, the electronic cigarette 60 can also include a sleeve assembly 87 removably and/or rotatably positioned about a first section 70 of the electronic cigarette 70. Moreover, the sleeve assembly 87 insulates at least a portion of the first section 70 so as to maintain the temperature of the aerosol prior to delivery to the smoker. In the preferred embodiment, the sleeve assembly 87 is rotatable about the electronic cigarette 60 and includes spaced apart slots 88 arranged transversely about the sleeve assembly such that the slots 88 line up with the air inlets 44, 44′ in the first section 70 to allow air to pass into the electronic cigarette 60 when a smoker draws a puff. Before or during smoking, the smoker can rotate the sleeve assembly 87 such that the air inlets 44, 44′ are at least partially blocked by the sleeve assembly 87 so as to adjust the resistance to draw and/or ventilation of the electronic cigarette 60 if desired.

Preferably, the sleeve assembly 87 is made of silicone or other pliable material so as to provide a soft mouthfeel to the smoker. However, the sleeve assembly 87 can be formed in one or more pieces and can be formed of a variety of materials including plastics, metals and combinations thereof. In a preferred embodiment, the sleeve assembly 87 is a single piece formed of silicone. The sleeve assembly 87 can be removed and reused with other electronic cigarettes or can be discarded along with the first section 70. The sleeve assembly 87 can be any suitable color and/or can include graphics or other indicia.

Aroma Delivery

As shown in FIG. 11, the electronic cigarette 60 can also include an aroma strip 89 located on an outer surface 91 of at least one of the first section 70 and the second section 72. Alternatively, the aroma strip 89 can be located on a portion of the sleeve assembly 87. Preferably, the aroma strip 89 is located between the battery of the device and the heater 14 such that the aroma strip 89 is adjacent a smoker's nose during smoking. The aroma strip 89 can include a flavor aroma gel, film or solution including a fragrance material that is released before and/or during smoking. In one embodiment, the flavor aroma of the gel, fluid and/or solution can be released by the action of a puff which may open a vent over the aroma strip when positioned inside the first section 70 (not shown). Alternatively, heat generated by the heater 14 can cause the release of the aroma.

In one embodiment, the aroma strip 89 can include tobacco flavor extracts. Such an extract can be obtained by grinding tobacco material to small pieces and extracting with an organic solvent for a few hours by shaking the mixture. The extract can then be filtered, dried (for example with sodium sulfate) and concentrated at controlled temperature and pressure. Alternatively, the extracts can be obtained using techniques known in the field of flavor chemistry, such as the Solvent Assisted Flavor Extraction (SAFE) distillation technique (Engel et al. 1999), which allows separation of the volatile fraction from the non-volatile fraction. Additionally, pH fractionation and chromatographic methods can be used for further separation and/or isolation of specific compounds. The intensity of the extract can be adjusted by diluting with an organic solvent or water.

The aroma strip 89 can be a polymeric or paper strip to which the extract can be applied, for example, using a paintbrush or by impregnation. Alternatively, the extract can be encapsulated in a paper ring and/or strip and released manually by the smoker, for example by squeezing during smoking the aroma strip.

In one embodiment, the electronic cigarette 60 of FIGS. 2, 5, 7 and 9 can also include a filter segment upstream of the heater 14 and operable to restrict flow of air through the electronic cigarette 60. The addition of a filter segment can also aid in adjusting the resistance to draw.

When the word “about” is used in this specification in connection with a numerical value, it is intended that the associated numerical value include a tolerance of ±10% around the stated numerical value. Moreover, when reference is made to percentages in this specification, it is intended that those percentages are based on weight, i.e., weight percentages.

Moreover, when the words “generally” and “substantially” are used in connection with geometric shapes, it is intended that precision of the geometric shape is not required but that latitude for the shape is within the scope of the disclosure. When used with geometric terms, the words “generally” and “substantially” are intended to encompass not only features which meet the strict definitions but also features which fairly approximate the strict definitions.

It will now be apparent that a new, improved, and nonobvious electronic cigarette has been described in this specification with sufficient particularity as to be understood by one of ordinary skill in the art. Moreover, it will be apparent to those skilled in the art that numerous modifications, variations, substitutions, and equivalents exist for features of the electronic cigarette which do not materially depart from the spirit and scope of the invention. Accordingly, it is expressly intended that all such modifications, variations, substitutions, and equivalents which fall within the spirit and scope of the invention as defined by the appended claims shall be embraced by the appended claims. 

We claim:
 1. An electronic smoking article comprising: a casing extending in a longitudinal direction; a mouthpiece; and at least one air inlet in communication with said mouthpiece, the at least one air inlet being operable to establish a predetermined resistance-to-draw under a prescribed test of said smoking article.
 2. The electronic smoking article of claim 1, wherein the casing is formed of a metal or a metal alloy and the at least one air inlet is formed in the casing.
 3. The electronic smoking article of claim 1, wherein the at least one air inlet is formed in a metallic plate insert arranged on an internal or external surface of the casing and which optionally superposes at least one air inlet formed in the casing.
 4. The electronic smoking article of claim 1, wherein the at least one air inlet has a width of less than about 2.0 mm and a length of less than about 1.5 mm.
 5. The electronic smoking article of claim 1, further including a removable protective covering which is positioned over the at least one air inlet after formation of the at least one air inlet and removed prior to smoking.
 6. The electronic smoking article of claim 1, wherein the at least one air inlet is operable to establish a resistance-to-draw during smoking of about 60 mm H₂O to about 150 mm H₂O.
 7. The electronic smoking article of claim 6, wherein the at least one air inlet is operable to establish a resistance-to-draw during smoking of about 90 mm H₂O to about 110 mm H₂O.
 8. The electronic smoking article of claim 1, wherein the air-inlet is positioned adjacent a connection fixture, the connection fixture including at least one slot corresponding with a location of the at least one air inlet.
 9. The electronic smoking article of claim 1, wherein the at least one air inlet is positioned adjacent a connection fixture, the connection fixture including an angled hole and a corresponding slot which communicate with the at least one air inlet.
 10. The electronic smoking article of claim 1, further comprising: an inner tube within the casing, the inner tube including a pair of opposing slots; a liquid supply comprising a liquid material, the liquid supply contained in an outer annulus between the casing and the inner tube; a coil heater located in the inner tube; a wick in communication with the liquid supply and surrounded by the coil heater such that the wick delivers liquid material to the coil heater and the coil heater heats the liquid material to a temperature sufficient to vaporize the liquid material and form an aerosol in the inner tube; and a power supply connectable to the coil heater and operable to apply voltage across the coil heater.
 11. The electronic smoking article of claim 1, wherein the inner tube has a diameter of about 4 mm and each of the opposing slots has dimensions of about 2 mm by about 41 mm.
 12. The electronic smoking article of claim 12, wherein the electronic smoking article comprises a first section attachable to a second section and wherein the wick, the liquid supply and the mouthpiece are contained in the first section and the power supply is contained in a second section.
 13. The electronic smoking article of claim 12, wherein the electronic smoking article comprises a single casing and wherein the wick, the liquid supply, the mouthpiece and the power supply are contained in the casing.
 14. The electronic smoking article of claim 12, wherein the inner tube is formed of woven fiberglass material.
 15. The electronic smoking article of claim 12, wherein the coil heater comprises at least one material selected from the group consisting of stainless steel, copper, copper alloys, nickel-chromium alloys, iron aluminum alloys, iron chromium alloys, superalloys, iron aluminides, nickel alumindes and combinations thereof.
 16. The electronic smoking article of claim 12, wherein the coil heater includes 4 turns to 8 turns, the turns being substantially uniformly spaced.
 17. The electronic smoking article of claim 12, wherein the power supply includes a battery.
 18. The electronic smoking article of claim 17, wherein the heater is connected to the battery by the electrical leads.
 19. The electronic smoking article of claim 12, wherein the first section and the second section have the same outer diameter and wherein first section is a disposable downstream section and the second section is a reusable upstream section.
 20. The electronic smoking article of claim 11, further including control circuitry including a puff sensor, the puff sensor operable to sense air flow and initiate application of voltage from the power supply to the coil heater.
 21. The electronic smoking article of claim 20, further including at least one secondary air inlet located adjacent the puff sensor.
 22. The electronic smoking article of claim 20, wherein the control circuitry further includes a heater activation light at an upstream end of the electronic smoking article, the heater activation light operable to light up when the heater is activated.
 23. The electronic smoking article of claim 12, wherein the liquid supply further includes a porous liquid storage medium operable to store the liquid material, the liquid storage medium is fibrous and comprises a material selected from the group consisting of rayon, polyester, polyethylene, cotton, ceramic, polyetheretherketone (PEEK) and combinations thereof.
 24. The electronic smoking article of claim 1, wherein the at least one air inlet is formed internally of the casing, the casing including a port, the port larger than the at least one air inlet.
 25. A method of improving a plurality of electronic smoking articles, the method comprising: forming an air inlet in an outer tube of each electronic smoking article, the air inlet being sized and configured to provide the electronic smoking article with a predetermined resistance to draw; and subjecting the air inlet of each smoking article to a test of resistance to draw during manufacture of the electronic smoking article.
 26. A method of improving a plurality of electronic smoking articles, the method comprising: forming an air inlet in a metal plate insert prior to placement of the metal plate insert into an electronic smoking article, the air inlet being sized and configured to provide the electronic smoking article with a predetermined resistance to draw; and subjecting the air inlet to a test of resistance-to-draw during manufacture of the electronic smoking article.
 27. The method of claim 26, further including affixing the metal plate insert to an inner or outer surface of the outer tube of the electronic smoking article.
 28. The method of claim 26, wherein the subjecting step includes establishing a benign test configuration.
 29. The method of claim 28, wherein the establishing step includes using a release connection between components of the benign test configuration, the connection conducive to automated machine handling.
 30. The method of claim 26, further comprising protecting the air inlet with a removable tape prior after the subjecting step.
 31. A method of achieving a consistent resistance to draw amongst a plurality of electronic cigarettes, said method comprising: determining a dimension of a critical orifice in an outer tube of an electronic cigarette that provides a desired resistance-to-draw; for each electronic cigarette, establishing the critical orifice by precision drilling the critical orifice in a wall of the outer tube of the electronic cigarette according to said determined dimensions and by selecting a material conducive to said precision drilling and having a capacity to retain said dimension; testing each established critical orifice for providing said desired resistance to draw and rejecting any established critical orifice failing said test.
 32. The method of claim 31, wherein the testing includes testing a critical orifice established on a piece separate of the electronic cigarette.
 33. The method of claim 31, wherein the desired resistance-to-draw is in the range of about 60 mm water to about 150 mm water.
 34. The method of claim 33, wherein the desired resistance-to-draw is in the range of about 60 mm water to about 150 mm water.
 35. The method of claim 34, wherein the desired resistance-to draw is in the range of about 90 mm water to about 110 mm water.
 36. The method of claim 31, wherein the testing includes monitoring the results of testing to detect trends away from said dimension of the critical orifice.
 37. A plurality of electronic cigarettes having a consistent resistance to draw, each of said plurality comprising: a precision drilled, critical orifice in an outer tube of each of a plurality of electronic cigarettes, the critical orifice having a dimension that provides a desired resistance to draw, the critical orifice precision drilled into a material having a capacity to retain the dimension, and each established critical orifice tested for providing the desired resistance to draw, wherein the plurality of electronic cigarettes are exclusive of any critical orifice having failed the test.
 38. An electronic cigarette operable to provide a consistent resistance-to-draw, the electronic cigarette comprising: a critical orifice in an outer casing operable to provide a desired resistance-to-draw; wherein the critical orifice is formed by precision drilling, has pre-determined dimensions and the outer casing is formed of a material conducive to precision drilling and operable to retain the predetermined dimensions of the critical orifice formed therein.
 39. The method of claim 38, wherein the desired resistance-to-draw is in the range of about 60 mm water to about 150 mm water.
 40. The method of claim 39, wherein the desired resistance-to-draw is in the range of about 60 mm water to about 150 mm water.
 41. The method of claim 40, wherein the desired resistance-to-draw is in the range of about 90 mm water to about 110 mm water. 